Mix the cake mix, flour, sugar, and salt together and set aside. In your mixing bowl, combine eggs, water, sour cream, and vanilla. Beat until blended, then add the dry ingredients until everything is mixed thoroughly.

Fill your cupcakes 1/2 full and pour remaining batter equally into 2 prepared 8" cake pans. Bake the cake separate from the cupcakes, approx. 40 min. Bake the cupcakes approx. 16 min. (If you wanted higher cupcakes, increase oven temperature to 350 and shorten the bake time.)

Check the doneness of both cake and cupcakes by tapping the top with your finger; if it springs back it's done.

Once cool, fill each cupcake with seedless raspberry jam (I use Wilton tip #230). For the cake, lightly frost the bottom layer and top with seedless raspberry jam. Place the 2nd cake layer on top and frost as usual. For a great frosting recipe, that makes enough for both the cake and cupcakes, see my Vanilla Buttercream Frosting recipe.